Well completion



D- 30, l952 T. s. wEsT 2,623,595

lvm. couFLETIoN Filed Oct. 23. 1945 4 Sheets-Sheet 1 ls I7' le e ,NVENTOR T. S WEST WELL COMPLETION Dec. 30, T1952 4 Sheets-Sheet 2 File( Oct. 23. 1945 Il III'nInlllrll il!!Ilfllilllnllllllllll Dec. 30, 1952 T, s,l WEST 2,623,595

WELL COMLETION Filed Oct. 23, 1945 4 Sheets-Sheet 5 lll lili

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T. S. WEST WELL COMPLETION Def. 30, 1952 4 Sheets-Sheet 4 Filed Oct. 23, 1945 INVENTOR. JAM., wwf

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Patented Dec. si), 1952 WELL COMPLETION Thomas S. West, San Antonio,

Tex., assignor of lM55/2000 to Blanco Oil Co., San Antonio, Tex., a corporation of Texas, and Z55/2000 to A. A.

Buchanan, San Antonio, Tex.

Application October 23, 1945, Serial No. 623,\989

s claims. (Cl. 16s-'1) l ducing formation. and any other material which might ow in with the oil or other fluid produced, is positively held in place. The result sought by such retention of material is not only the prevention of sanding up" of tubing or other equipment, but also the prevention -of deeper penetration of the producing formation resulting from the removal of sand, or the development of channels upward to gas zones or other undesired formations because of sand production, or the flowing out of the mud iilter cake commonly present between the cement behind the casing and the well wall.

Another object of 'this invention is to provide a positive means of plugging back up the well bore to produce from a higher portion of the strata if the .producing formation has been penetrated too deeply. The invention also contemplates a positive method of sealing the space between the screen or liner and wall of the well immediately above the level from which produc tion is desired.

An additional object of this invention` is to provide a satisfactory method whereby the gravel may be placed in high pressure wells without completely displacing the drilling mud used in the usual rotary method, and at the same timeavoiding the `saturation of the gravel pack with mud while also leaving a permanent lter cake between the gravel and the producing formation.

It is a further object of this invention to provide a method of, and apparatus for, placing gravel in wells which permits the accurate plac- `tion about the well bore; for prevention of deeper penetration of the producing formation; the producing of upward channels by sand production; or the flowing out of the filter cake, do not appear to have been previously recognized. The production of a relatively small amount of sand or nlter cake may be suilicient to produce a channel for ilow of water from a lower level, or gas from an upper level, in a given sand.

However. a gravel pack arrangement which is satisfactory from the standpoint of preventing sanding up. or operating dimculties, may not, therefore, be effective in preventing the production of channels and associated excessive water production or high gas-oil ratio. Likewise, gravel pack arrangements which are successful for producing sands containing only one iluid, such as is usually the case with water wells. may not be satisfactory for selectively producing one fluid from a sand containing two or three different iluids at different levels; such as, sands containing gas. oil. and water. f

This invention provides a gravel pack arrangement in which the gravel is held securely in place in such way as to prevent movement of gravel in any direction, thus avoiding the production of channels in the gravel through which sand might flow.

Previous gravel pack methods do not provide a positive means of avoiding the existence of unnlled cavities in the gravel packed section into which gravel may move; such as, the space resulting from bridging of gravel. or because the gravel is deposited by the circulation method. Space may also exist between the top of the gravel and the packer used to seal the space between the liner and casing, or in the case of the use of ing of relatively thin layers or strata of gravelI sand, cement, or other materials.

Still further objects of this invention are to provide a simple and eillcient means for placing, and approximately centralizing, the screen or liner in the well. with a means, that may later be removed while preventing the entry of material from the well bore into the liner while gravel or cement is being placed.

The use of gravel for retaining sand.' or other producing formation substances from the sanding up of the tubing, pumping equipment, and other apparatus, is well known to the art. The desirability of retaining the sand 9i' the formagravel having less density than the well duid, between the bottom of the pack" and the bottom of the well.

This invention provides an effective method of plugging back in a well bore which has heretotore been very dimcult if not practically impossible to attain in unconsolidated sands or sands having low tensile strength. Attempts to plug back in such types of sands with cements or plastics have usually failed because sand production results in the formation of a channel along the outer face of the cement or plastic plug. The existence of a mud filter cake between the cement, or plastic, and the wall of the well may also result in failure of such a plugging procedure because the lter cake flows out when the pressure gradient along the face thereof becomes sumciently great.

This invention provides a procedure for creatinga plug which tends to be self-sealing, whereas with other processes any leakage past a cement or plastic plug tends to create a channel and enlarge with flow rather than to maintain a seal. The present type of plug may also be applied with equal effectiveness for sealing the space around the liner and also in the area immediately above the zone from which production is desired.

Other and further objects of the invention will be readily understood when the following description is considered in connection with the drawings wherein:

Fig. 1 illustrates the method employed for conditioning the well in some cases.

Fig. 2 is a sectional view taken along line A-A of Fis. 1.

Fig. 3 shows the slotted liner, or other screen, in place and illustrates the method of depositing and tamping gravel around this liner. Fig. 3 also illustrates the apparatus employed for depositing materials as gravel or cement.

Fig. 4 illustrates the completed gravel packed liner in a casein which the well has been plugged back.

Fig. 5 ilustrates the completed gravel pack in which the plugging arrangement has been placed above the zone from which production is desired.

Fig. 6 shows an additional step in the herein described gravel packing procedure which is desirable if caving is likely to occur while gravel is being placed.

Referring to Fig. 1, l represents the original wall of the well bore as it is drilled. The well casing is designated by 2; and the cement filling, the space between the outside of the casing. and wall of the well by 4. The producing sand is designated by 3. In wells drilled by the rotary method, a filter cake shown at 5 is formed on the face of the permeable formations by the weight of the column of drilling mud which forces liquid from the mud back into the formation which acts as a filter for the solid material in the mud so that a layer or facing of such solids is formed around the well bore. Similar lter cake in the section to be gravel packed is shown at I. The bailer employed for dumping liquid in the zone to be gravel packed is designated by l. This bailer is lowered into the well by wire line 1, its lower end being closed by one or more discs I5 of glass, porcelain, cement, plastic, certain metals, or other frangible material. Plate glass has been found to be very satisfactory for this purpose. Such disc I5 is broken by a breaker l1 when the breaker is forced against the bottom of the well. 'Ihe breaker Il is supported by the member I8, which is welded or otherwise attached to shoe Il on one end, and which provides on the other end a rigidly attached vertical bushing of such inside diameter as to permit free vertical movement of breaker I1. Breaker I1 may be of any desired length. thereby permitting the dumping of bail'er l above bottom. When bailer 8, including breaker I1, reaches the bottom of the well, the jar or piston I moves downward, striking the upper end of piston rod Il, thereby shearing the shear pin I0. This permits the downward movement of piston lI--this piston being preferably made of rubber or of similar material. Piston rod Il and piston I8 are of such dimensions and material as to have sumcient weight to result in positive downward movement of I3 and expulsion of liquid Il from the lower end of bailer l. A detachable wall scratcher, or underreamer I6, is attached to the lower end 4 c wall scratcher II may be omitted when it is desired to run bailer l without wall scratcher action.

Prior to the gravel packing operation illustrated by Figs. 3, 4, and 5, it ls desirable, but not always essential, to remove all drilling mud. filter cake, and any other material which might result in clogging of the gravel, from the zone in which gravel is to be placed. This may be-accomplished by three principal methods:

(l) If the sand to be gravel packed does not have sufficient pressure to result in a flow of fluid from the well. fluid may be removed from the well by operations such as hailing, swabbing or pumping, until all undesired material has been removed from the zone into which gravel is to be placed.

(2) The well may be filled with a fluid or solution which does not contain any undissolved solid material. The filter cake on the face of the sand may then be removed by mechanical means; such as by a wall scratcher or underreamer. or by means of chemicals. Filter cake removed may then be brought to the surface by circulation, or by bailers and the like. To provide a fluid having sufllcient weight to control high pressures, solutions of various concentrations and substances may be employed. The following solutions have been lfound satisfactory and economical for producing solutions of the indicated weights:

Pounds per gal.

Aqueous sodium chloride solutions--- 8.33 to 10 Aqueous ferric sulphate, chloride, or

nitrate solutions 10. to 14 Aqueous zinc chloride or bromide 14. to 17 (3) The well may be filled, or partially filled, with a fluid containing solid material which forms a filter cake, but which may be removed after the gravel has been placed. A starch. prepared in a saturated solution of a substance with an excess quantity of the solute added in the form of a powder, has been found satisfactory for this purpose. Because of lower cost, a starch prepared in.a saturated aqueous sodium chloride solution, to which powdered or finely ground sodium chloride has been added, has usually been found preferable. Ferrie salts, zinc chloride or bromide, or other salts producing heavy solutions may also be used instead of sodium chloride. 'I'he starch contained in the filter cake may be converted to a glucose fluid of low viscosity, mainly as a result of hydrolysis due to, the action of concentrated hydrochloric, sulfuric, nitric, or other strong acids. At temperatures above approximately 150 F., the starch may also be hydrolyzed by weak acid solutions, such as 'l per cent or less hydrochloric acid. or at lower temperatures bythe action of starch splitting enzymes. such as amalyase. The required enzyme may be a commercial product. such as pancreatin, or may be produced by action of microorganisms or bacteria placed in the starch; such as, Bacillus m'ndulus, Bacillus meaatherium, or Bacillus subtilis. After the starch has been decomposed, the powdered salt contained in the filter cake is dissolved by the now of the water which has filtered into the sand from the well, either from water purposely forced into the sand prior to use of the starch solution, or by water which has invaded the sand from the drilling mud during the usual drilling operation.

In using the apparatus and procedure illustrated by Fig. l for preparing a well for gravel packing, it has been found preferable, from the or bauer s for use in removing .nl fer sek? I- The standpoint or economy. to olooe only a sumcient quantity of starch solution to iill a relatively short distance above the sand, such as 100 feet, by means of the dump bailer 9. After depositing the desired amount of starch solution water containing acid for hydrolysis of starch, a starch splitting enzyme, or micro-organism capable of decomposing starch, is dumped opposite the sand by means of the dump bailer 9. Starch solution and water may also be placed by pumping down through the drill pipe or tubing. Filter cake I is then removed by action of a wall scratcher or by underreaming. 'I'he removal of iilter cake allows the water containing the starch splitting substances to flow into the sand. When this water has i'iowed into the sand, the starch'y powdered-salt solution reaches the sand and builds up a lter cake composed of starch and powdered salt on the face of the sand. It is usually desirable at this time to recover any iilter cake, or cavings which may be present in the bottom of the well, by means of a bailer, sand pump, or

vsimilar procedure.

Fig. 3 illustrates the gravel packing, procedure in an oil well in which the oil sand section 3 has been penetrated to a water saturated section 32. Layers 23, 30, and 3| provide an impermeable plug for preventing the upward flow of water in the well.

Layer 3| consists of a relatively coarse gravel which is saturated with drilling mud, or other fluid-solid mixtures capable of depositing a filter cake of low permeability on a sand when the fluid phase flows into the pore spaces of the sand. The size of gravel in layer 3| must be such as to provide sufficiently high permeability to permit the ow oi drilling mud contained in the pore spaces. If drilling mud, of the characteristics usually employed with the rotary method of drilling, is used, gravel passing a one-half inch mesh screen and which is retained on a one-quarter inch mesh screen has been found satisfactory.

Layer 30 is composed of cementing material; such aS, gypsum or Portland cement, plastic, or the like. To prevent the downward ow of this cement into layer 3|, gravel of such size as to bridge the pore spaces of the gravel of layer 3| is preferably mixed with the cementing material.

After the cement material of layer 30 has hardened, a layer of sand, or other iinely divided material 28, is placed on top of layer 30. 'I'he particle size of this layer is such as to result in a filter cake of low permeabilityif the fluid phse of the wall building material contained in layer 3| rlows into its pore spaces.

Layers 29, 30, and 3| are preferably deposited by a dump bailer arrangement such as that illustrated in Fig. 1. Wall scratchers I6 are preferably removed when employing the bailer 9 for this purpose. The piston I3 may also be omitted for this service.

If cement layer 30 does not providev an impervious plug, the upward flow of fluid results in a flow of the wall building material of layer 3| s through any crevice which might be present and the depositing of a substantially impermeable nlter cake on the bottom face of sand layer 22. It is thus evident that this plugging arrangement tends to be self-sealing, whereas any path of now which develops with usual cement, plastic, or

other plugs tends to enlarge with ilow rather than seal. It is evident that cement layer 30 is not essential to satisfactory action but rather improves the emciency of the plug by decreasing the cross sectional area which must be sealed by filter cake deposition.

If oil sand 3 has not been penetrated too deeply. layers 23. 3l. and 3| are not required. In either case it is preferable. but not essential. to dump a thin layer of gravel 28 prior to the lowering of liner Er screen 2i to avoid the possibility that this liner might penetrate sand or other material which might be present in the bottom of the well suiliciently to permit ilow of this material into openings 2l. Liner 28 is then positioned in the well as illustrated in Fig. 3, preferably by lowering on a wire line by means of a tool which permits its release after reaching the desired level. Various such devices are known to the art. An overshot. of the type used in retrieving wire line core4 barrels and which may be released by dropping a short length of pipe down the wire line, has been found to be a satisfactory method of placing liner 25. Liner top 23 of Fig. 3 is formed to permit engagement by. and release from. this or other type of overshot. Liner 25 may also be placed by means of tubing or drill pipe, or it may be dropped from the surface. It will also be noted from Fig. 3 that liner top 23 is held in place by the shear pin 2l. This pin 24 is of such material and diameter as to be sufficiently strong to support the weight of liner 25 with a liberal safety factor, but not so strong as to prevent shearing before failure at other points, when an upward pull is exerted on the wire line 1 with the overshot engaging the top 23 after the liner 25 has been cemented in place as shown by Figs. 4 and 5.

After liner 25 has been positioned, it is preferable to approximately centralize it by lowering the dump bailer 9, with the frangible disc l5 removed, until it passes over 28 and reaches the bottom. Gravel is then deposited around liner 25 by means of the dump bailer 9. This gravel 2| is poured into the bailer 3 through window I2 after the frangible disc i5 has been secured between the shoe end I5 and shoulder Il. The bailer 3 is then lowered by means of the wire line 1 and suitable hoisting apparatus. When the foot piece 22 passes over the liner 25, the liner top 23 breaks the frangible disc I5, allowing the gravel 2| to settle around the liner 25. The downward movement of bailer s is continued until the surface of gravel 28 is reached. By alternately raising and lowering bailer 3, the gravel 2l is firmly tamped around the liner 25. 'I'he jar 8 may also be employed to aid in the tamping operation: also to provide a means of freeing the bailer 3 by upward jarring if it should become stuck; and to facilitate the breaking of the relatively strong frangible discs. The point at which the bailer "picks up oil bottom is preferably determined after each deposit of gravel is made. either by means of a suitable weight indicator or by observing or "feeling the sudden increase in tension of the wire line 1 as the bailer I is lifted.

v to avoid invasion of gravel 4|.

7 particles will be absent or negligible. The optimum size of gravel to be employed in a particular case may be inferred by sieve analysis of the sand. Usually it is preferable, however, to determine optimum gravel size by placing the sand to be screened and the gravel under test in contact in a suitable cell. and flowing oil, water, or gas through this cell to observe the resulting invasion of the gravel by sand. The size of liner slots or openings 25 are such as to effectively pre- `vent the entry of the gravel 28 into the liner 25. The screen portion of the liner 25 may be of any of various types known to the art, including a screen which has been pre-packed with gravel or other filtering material.

After the desired quantity of gravel 22 has been placed around liner 25, a cementing material is dumped around the liner 25 and on top of the gravel 29 by means of the dump bailer 9. 'I'he cement material used for this purpose may be any cement which has suillcient strength and resistance to corrosion under the conditions existing 4in a given well; such as, gypsum cement, Portg land cement, or plastic. To prevent the flow of cement into the gravel, it is preferable to mix with the cement, sand or other material which will bridge the pore spaces of the gravel 29. The volume of cement placed is preferably such that the liner 22 is not covered with cement.

After cement 21 has hardened, the wire line overshot employed in lowering the liner 25, or another suitable shing tool, is lowered until liner top 22 is engaged. Shear pin 24 is then sheared by pulling upward on the wire line 'l and the liner top 22 is brought to the surface.

It has also been found satisfactory, but less efficient from the standpoint of time, to completely cover the liner top 22 with cement. As the liner top 22 is preferably made of an easily drillable metal such as aluminum alloy on cast iron, after the cement has hardened, it may then .be drilled out until the portion of the liner top 22 which protrudes above the hner 25 has been removed.

The removal of liner top 22 opens a path for iiow of the fluid, or fluids, which the sand 2 yields so that such fluid, or uids pass from the sand 2 through the gravel 22; and out through the slots, or perforations 26. of the liner 25 into the overlying well space. This fluid is then broughtv to the surface by flowing, pumping, or any of the various methods of producing wells known to the art. I

If it is desired to prevent the downward flow of fluids from the portions of the sand lying above the zone in which completion is desired, the arrangement shown in Fig. is employed. In Fig. 5. the sand zone 25 may, for example, represent gas saturated sand; and the sand zone 28, oil saturated sand. Layers 29, 49, and 4| are similar to layers 2|, 22, and 29. of Figs. 3 and 4, respectively. That is. layer 29 is a relatively coarse gravel having its pore spaces lled with a substance or mixture capable of forming a nlter cake of low permeability on porous media of suitable particle size such as drilling mud, mixtures of heavy oils with cement, or other nely divided solids. Layer 40 is composed of cement such as gypsum or Portland cement or plastics. Layer` 4I is composed of sand or similar finely divided material. Layer 4| is preferably of as low permeability as possible consistent with a particle size, or range o! particle sizes, required The preferred 4|, 4l, 29, and cement layer 21 is the same as previously described in connection with Figs. 3 and 4, except that the sequence in which the various layers are placed differs.

If a ilow of nuid downward through layer 29 occurs, as might be the case if layer 40 should contain cracks or be imperfectly bonded to sand 28, the wall building material contained in layer 29 flows through such openings and deposits a illter cake oi low permeability on layer 4l, thus providing a self-sealing action.

An additional function of the arrangement shown in Fig. 5 is the securely holding in place of filter cake layer 25 which is commonly present between cement 22 and sand 25 and 28, thus avoiding an unobstructed path for uid flow along the face of sand 25. This is accomplished by preventing the Production of sand 2B and 22 which in turn holds filter cake 25 in place. Since filter cake 25 is usually semi-nuid in nature, the development of a sumciently high pressure gradient results in its flowing out unless some means of holding it in place is provided. l v

Obviously, layers 29, 2li, and 2| of Figs. 3 and 4, or layers 4I, 40, and 29 may be omitted if :lesired. For example, the sand may be entirely saturated with the uid which it is desired t0 produce, or the thickness of this zone may be suillciently great as to render unnecessary the prevention of flow in the vertical direction immediately above or below the zone being produced. Various combinations of layers 29, 40, and 4i, or 2|, 25, or 29 may also be employed. For example, layers 20 or 40 may be omitted and sealing obtained by deposition of filter cake on layer 29 or 4| by the wall building material contained in layer 2l or 29. Layers 29 and 4i, or 2| and 29, may also be omitted and the entire space occupied by these layers filled with cement. 0bviously, layers 2i, 2li, and 29 and 29, 40, and 4I may both be used in connection with gravel pack 22, or 42, in a given completion.

Fig. 6 illustrates an additional step in the placing of grav'el which is desirable if caving is likely to occur while the gravel is being placed, or if the screen should sink into loose cavings, in the gittom of the well, to the level of the first open- Liner top 22, of Fig. 3, has been modified so as to permit the flow of huid from liner 53 (Fig. 6), but the entry of material into the liner is prevented. 'I'his is accomplished by valve 49 and associated part 42. Part 48 is formed so as to permit attachment to liner 52 by means of shear pin 50. After-gravel 55 has been packed around liner 52 to a desired height, hydrostatic bailer 46 is lowered into the illustrated position. 'I'rip valve 41 closes the lower portion of this bailer against fluid entry. Since valve 41 is usually set with atmospheric pressure in the bailer space above 41, the pressure tending to cause flow into the bailer will be equal to the pressure in the well at the level of the bailer. Packer 5i, which is constructed of rubber or similar material, passes over liner 52 to a distance determined by the position of trip valve 41. When valve 41 is tripped, there results a iiow of uid from the inside of liner 52 into bailer 46. Any sand, or other material of fine particle size which might be present around the screen portion of liner 53, flows into 52; and gravel 55 ows into the resulting space.

It is evident that the ilow of uid from the well procedure for placing liner 42, gravel 42, layers space immediately above into gravel55 will tend 9 to move this gravel into anyexisting cavities. Because of the relatively high pressure which may exist in deep wells, the force thus available for forcing gravel into cavities may be considerable. After the space outside of liner I3 has been filled to a height above the screen portion of liner Il, the flow of fluid downward through gravel 55 may be reduced by placing a layer of ilnesand on top of gravel Il. This sand layer performs the additional service of filtering out any solids which might result in the plugging of gravel It. Buch sand layer should, of course, be of such particle size as to be effectively retained orscreenedbygravelli.

After the desired amount of fluid and other material has owed from liner It by the use of bailer Il as above described. the gravel packing procedure is completed by dumping additional material, including a layer of cementing material, around liner $3 on top of gravel i! as previousLv described in connection with Figs. 3, 4, and 5. After cementing material has set, liner top 48 may be engaged by a suitable fishing tool and removed by shearing pin Il.

Obviously, the application of "suction" to liner 53 by bailer 48 could be applied at various stages of the operation, including the period immediately following the depositing of cement. The magnitude of suction applied may be controlled by varying the volume of the portion of bailer IB above trip valve 41, or by variation of initial pressure within this space.

It is evident that similar flow through gravel 55 into screen 54 may be produced at a greater expense of labor by placing trip valve mechanism 4l and packer Il on the lower end of tubing or other pipe extending to the surface.

In the use of the procedure of Fig. 6 with relatively short liners, it is usually desirable to place a flange or other projection on the bottom of liner 53 to reduce the possibility of pulling the liner out of gravel Il when bailer 4I is raised.

I claim:

l. The method of well completion which comprises the positioning. at a desired level in the well, of a screen member having a removable top closure, the filling of the space between the screen member and a fluid producing formation with a filtering material, the illling of the well space between the screen member and the well bore and above and in surface contact with the filtering material with a cementing material, and the removing of the top closure to provide a path for uld flow from the screen member into the overlying well space.

2. Apparatus for gravel packing a well comprising, a dump bailer including a tubular body adapted to receive therein material to be deposited in the well, said bailer having a frangible bottom and being adapted to be lowered into a well, a tubular member adapted to be positioned at the bottom of the well and being of a size to permit said bailer to pass thereover to the bottom of the wall and having a perforated lower section and a removable top closure to guide said bailer over said tubular member and to fracture said frangible bottom, the interior of said bailer body being suiilciently larger than said tubular member so that said material may flow out through said fractured bottom into said well around said tubular member.

3. The method of well completion which comprises, the positioning, at a desired level in the well acacent a fluid yielding formation, of a l0 screen'member having a removable top closure and a perforate portion below the top closure, the providing of a vessel having a frangible bottom and containing a filtering material, the lowering of the filled vessel into the well until its bottom is fractured by contact with the top closure and the filtering material surrounds the perforate portion and the screen member to a desired height. the raising and then lowering of the vessel over the screen member to tamp the ltering material,- the raising of thevessel to the top of the well and placing a new frangible bottom therein, the placing of cement in the vessel, the

lowering of the vessel into the well until its bottom is fractured by contact with the top closure and the cement is positioned around the screen member on top of the ltering material and to a desired distance below the top of the screen member, and the removal of the top closure from the screen member.

4. Well completion apparatus including, in a well bore, a screen member having a perforate and a non-perforate section, a filter pack filling the well space between said perforate section and the well bore wall, a first layer of cementing material, a second layer of granular material immediately overlying said nrst layer and composed of particles of different sizes and being substantially impermeable to the flow of well fluids, said filter pack constituting a third layer of granular material immediately above said second layer and surrounding said perforate section, the particle size of said filter pack being such as to be retained outwardly of said screen member and to form pore spaces which retain the particles of said second layer and the particles of fluid yielding formations bounding the wellbore, and cementing material above said lter pack and nlling the well space surrounding said non-perforate section to a desired distance below the upper end of said screen member.

5. Well completion apparatus including, in a well bore, a screen member having a perforate and a non-perforate section, a rst layer of granular material composed of particles of different sizes and being substantially impermeable to the flow of well iluids, a filter pack lling the well space between said perforate section and the well bore wall, said lter pack constituting a second layer of granular material immediately above said first layer and surrounding said perforate section, the particles size of said filter pack being such as to be retained outwardly of said screen member and to form pore spaces which retain the particles of said nrst layer and the the well bore, and cementing material above said filter pack and filling the well space surrounding said non-perforate section to a desired distance below the upper end of said screen member.

6. Well completion apparatus including, in a well bore, a screen member having a perforate and a non-perforate section, a filter pack filling the well space between said perforate section and the well bore wall, a rst layer. of coarse granular material between the well bore wall and said nonperforate section and being impregnated with a iiuid containing solid particles of such size as to flow through the pore spaces, a second layer of ne granular material lling the well space between said non-perforate section and the well bore wall and between said filter pack and said rst layer, the particles of said second layer being of such size range as not to eectively enter the pore spaces of said lter pack and said rst layer 11 while forming pore spaces sufhciently small to prevent the entry thereinto of the said solid particles contained in the fluid impregnating said nrst layer, and means to hold said iter pack and said layers firmly in place.

7. Well completion apparatus including, in a well bore, a screen member having a perforate and a non-perforate section. a filter pack filling the well space between said periorate section and the well bore wall, said filter pack comprising a lower first -layer of granular material filling the well space between said perforate section and the formation bounding the well bore, a second layer of granular material immediately overlying said filter pack and filling the well space'between said non-perforate section and the well bore wall. said second layer being composed of particles of different sizes and being substantially impermeable to the ow of uids but which contains particles sumciently large to prevent the movement of said second layer into the inter-granular pore spaces of said filter pack, a third layer lcomposed of a cementing material immediately overlying said second layer and filling the well space between said non-perforate section and the well bore wall to a desired distance below the upper end oi' said screen member.

8. Well completion apparatus including, in a well bore, a screen member having a periorate and non-perforate section, a filter pack filling the space between said perforate section and the well bore wall, a first layer of coarse granular material impregnated with a fiuid containing solid particles of such size as to pass through its pore spaces, a second layer composed of cementing material immediately overlying said first layer, a third layer of granular material immediately overlying said second layer, the particles of said third layer being of such size range as not to effectively enter the pore spaces of said filter pack and to form spaces through which the fluid containing solid particles in said iirst layer will not flow, said lter pack immediately overlying said third layer and nlling the well space between said perforate section o! said screen member and the formation bounding said well bore, and a layer of cementing material immediately overlying said filter pack and filling the well space between said non-perforate section and said well bore wall to a desired distance below the upper end of said screen member.

9. Well completion apparatus including. in a well bore, a screen member having a periorate and non-perforate section, a lter pack lling the well space between said perforate section and the well bore wall, a nrst layer of coarse granular material impregnated with a fluid containing solid particles of such size as to pass through its pore spaces, a second layer composed of granular material overlying said first layer and underlying said filter pack, the particles of said second layer being of such size range as not to eii'ectively enter the pore spaces of said nlter pack or the pore spaces of said first layer and to form inter-granular pore spaces through which the fluid containing solid particles in said first layer will not eflectively flow, and a layer of cementing material immediately overlying said filter pack and filling the wall space between said non-perforate section and the well bore wall to a desired distance below the upper end of said screen member.

THOMAS S. WEST.

REFERENCES CITED The following references are of record in the file of this patent:

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